1. Field of the Invention
The present invention relates to a flash memory device, and particularly to a flash memory device having a program verification circuit and a pull-up circuit which enable a verification of a state of a memory cell before performing a pre-program operation.
2. Information Disclosure Statement
In general, the flash memory device such as a flash electrically erasable and programmable read only memory (EEPROM) comprises a memory cell array and peripheral circuits. The memory cell array is divided into a plurality of sectors, and in each sector a plurality of memory cells are connected in a matrix fashion between a bit line and a word line. The peripheral circuits are constructed in such a way that it programs or erases the memory cells according to signals input from external or reads data programmed in each memory cell and outputs the data to the external. Such flash memory device has functions of electrical programming and erasing, and performs a verification operation to confirm whether the memory cells are programmed or erased after operation of programming or erasing. Here, the programming operation is performed byte by byte or word by word, and the erasing operation is performed chip by chip, that is, for a total of sector or memory cell. In addition, the flash memory device performs an operation of pre-programming the memory cells to prevent an over erase of memory cells before performing the erasing operation. In a conventional flash memory device, since the pre-program operation is performed byte by byte or word by word, the pre-program operation takes long time. Furthermore, in case where the memory cells which keep the program state are reprogrammed by the pre-program operation, the reliability of the memory cells can be degraded by an over programming.